A Yale School of Medicine neuroscientist has succeeded in keeping brains from the severed heads of pigs alive for up to 36 hours.

Dr. Nenad Sestan revealed the research, which has been conducted on between 100 and 200 pigs’ brains, at an ethics conference held March 28 at the National Institutes of Health, according to MIT Technology Review. Sestan is a professor of neuroscience, comparative medicine, genetics and psychiatry.

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A staff member in Sestan’s lab said Sestan would not talk publicly about his work until it is published in a peer-reviewed journal. MIT Technology Review reported that Sestan said he had not intended the information to become public.

Stephen Latham, director of the Yale Interdisciplinary Center for Bioethics, cautioned about thinking of the brains as “alive.”

“The brain is not conscious,” he said. “It’s not a pig brain in a vat wondering where it is. … It isn’t the sort of sci-fi thing where you wake up and think, ‘I can’t see anything or feel anything.’”

However, the MIT Technology Review article reported, “in what Sestan termed a ‘mind-boggling’ and ‘unexpected’ result, billions of individual cells in the brains were found to be healthy and capable of normal activity.”

The brains, which MIT Technology Review reported were obtained from a slaughterhouse, were kept alive by circulating fluid through a system of tubes and reservoirs called BrainEx, which carried oxygen to the brain stem, the cerebellar artery and other parts of the brain.

That, however, is not the same as consciousness, Latham said, but is more similar to the cells in other parts of the body remaining alive after a person has died.

“When you die … a bunch of your cells in your body would still be alive for some time in the biological sense of being alive,” Latham said. But once the heart stops pumping blood, cells — including brain cells — begin to die.

“What Dr. Sestan is doing is trying to remove that cellular death” in order to conduct research on the whole brain. “Suppose someone were testing a new drug for some brain disease,” such as Alzheimer’s disease, which is associated with protein fragments, called plaques, that form between nerve cells in the brain. “He could introduce that drug into the brain to see what effect it has on brain tissue,” Latham said.

Research could also include “the fine mechanisms of how oxygen is distributed through brain tissue,” Latham said. “The opportunity to have a brain that isn’t decomposing … has a lot of promising uses in understanding brain and brain diseases.”

Latham said there could be ethical issues — as well as immense practical ones — if the technology were used on human brains, such as those from bodies donated for scientific research. Brain damage results if someone lacks oxygen for four minutes, he said.

“Dr. Sestan’s technique, in theory, could sustain a brain, but we’d have to figure a way to get a functioning brain hooked up to a machine in practically no time at all,” Latham said. He said some of the brain cells in the pigs Sestan used would have died during the process of slaughtering the animal, removing the brain and connecting it to the machinery.

Ethicists would have to contend with how a brain being kept alive outside the body differs from someone who is in a persistent vegetative state and lacks consciousness but is kept alive by being put on a ventilator and given nutrition through a feeding tube.

Researchers in his lab tested the possibility of the brains’ regaining consciousness by attaching electrodes to them, but they found no activity, the article said.

“We think it’s incredibly important work” and could lead to a great deal of new information about the brain, said Nita Farahany, an associate professor of law and of philosophy at the Duke University School of Law, whose expertise is in bioethics, biosciences and technology.

Farahany was the first author of an April 25 commentary on the website of the journal Nature on “the ethics of experimenting with human brain tissue.” While the comment, written with 16 other experts, including Sestan, did not specifically address his work, it dealt with the implications of experimenting on human tissue such as brain organoids, which can be created by signaling human stem cells to develop into brain tissue, or on samples of brain tissue removed during surgery.

Sestan’s work “raises some profound ethical questions that need to be addressed in order to allow the responsible progress of the science,” Farahany said. But she added, “the problem is this is unpublished research. … It’s difficult to comment. I think the MIT Technology Review was irresponsible to publish to begin with. There are more research studies and issues you would want to address before you did this research in humans.”

Farahany said the best course would be to “allow the paper to be published” and then the ethical implications could be better addressed.

MIT Technology Review did not immediately respond to a request for comment.

“To be fair to Dr. Sestan, he has been engaging in those ethical conversations from the get-go,” she said. He is aware of “the ethical quandaries that the research could raise, and he is deeply committed to being part of those conversations.”

But she said “all of this research is really in service of understanding how the brain works. … Studying an intact post-mortem brain may be better than studying pieces of a brain.”

Yale spokeswoman Karen Peart issued a statement Tuesday, saying: “Dr. Sestan will comment on the findings when they are published. The university fully supports the work of all of its researchers, including work that has the potential to lead to the development of tools that aid brain function and recovery.”